Lightr

A lightweight, self-hosted email server written in Go. Single binary, multi-domain, full-stack email.

The Problem

Self-hosting email is notoriously painful. Existing solutions like Postfix + Dovecot require stitching together multiple daemons, writing cryptic config files, and constantly fighting deliverability issues. Managed email is expensive at scale, and privacy-conscious users or small teams often have no middle ground between Gmail and a week-long sysadmin headache.

The Solution

Lightr is a complete email server in a single Go binary. It handles SMTP (inbound and outbound), IMAP (for email clients), and exposes a REST API for programmatic management. Everything runs off SQLite — no external database required.

How It Works

1. SMTP Receiver — Accepts inbound email, parses MIME structures, and stores messages in per-account mailboxes
2. SMTP Relay — Sends outbound email with automatic DKIM signing for deliverability
3. IMAP Server — Lets standard email clients (Thunderbird, Apple Mail, etc.) connect and manage mailboxes
4. REST API — Create organizations, domains, accounts, and templates programmatically
5. Email Queue — Persistent queue with exponential backoff for failed deliveries

Key Features

• Single Binary — Download, configure, run. No runtime dependencies
• Multi-Domain — Host email for multiple domains with per-domain TLS via SNI
• DKIM Signing — Built-in key generation and automatic outbound signing
• IMAP Access — Full IMAP server for standard email clients
• REST API — Complete HTTP API for domain, account, and template management
• Email Queue — Persistent outbound queue with retry and backoff
• Open/Click Tracking — Pixel tracking for opens, redirect tracking for clicks
• Webhooks — Notify external services on email events (delivery, bounce, open)
• Bounce Handling — Automatic bounce processing and feedback loops
• Rate Limiting — Configurable rate limits per account and domain
• TLS Everywhere — HTTPS, SMTP STARTTLS, and IMAPS with Let's Encrypt support
• SQLite Storage — Zero-dependency, file-based storage with blob attachments
• Multi-Tenant — Organization-level isolation for SaaS or agency use
• Systemd & Docker — Runs as a service or in a container

Technical Stack

• Go 1.24 — Single-binary builds for any platform
• go-smtp — SMTP protocol implementation (emersion/go-smtp)
• go-imap v2 — IMAP server implementation (emersion/go-imap)
• go-msgauth — DKIM signing and verification
• SQLite — Embedded database via modernc.org/sqlite (pure Go, no CGo)
• Cobra — CLI framework
• YAML — Human-readable configuration

Usage

# Install via quickstart
curl -fsSL https://raw.githubusercontent.com/nigelbasa/lightr/main/quickstart.sh | sudo bash

# Or build from source
go build -o lightr ./cmd/lightr

# Initialize (creates config, generates API key)
lightr init

# Create an organization and domain
lightr add-org --name "My Company"
lightr add-domain --org <id> --name mail.example.com

# Generate DKIM keys (outputs DNS TXT record to add)
lightr dkim-gen --domain mail.example.com

# Create an email account
lightr add-account --domain <id> --email user@mail.example.com

# Start the server
lightr serve

# lightr.yaml — minimal config
data_dir: ./data

http:
  addr: ":8080"

smtp:
  addr: ":2525"
  domain: "mail.yourdomain.com"

imap:
  addr: ":1143"

dkim:
  selector: "default"
  key_bits: 2048

Architecture

Lightr's internal structure follows a clean domain-driven design with 37 packages covering the full email lifecycle:

• smtp/ — SMTP server, relay, and DKIM signing
• imap/ — IMAP server implementation
• api/ — REST API handlers
• queue/ — Persistent email queue with retries
• storage/ — SQLite database and blob storage
• tracking/ — Open/click tracking
• webhook/ — Event notification system
• bounce/ — Bounce processing and feedback loops
• filter/ — Email filtering rules
• ratelimit/ — Per-account and per-domain rate limiting
• security/ — TLS, authentication, and encryption

Why I Built This

I needed email infrastructure for my own projects — transactional emails for Inzwi, school communications for Nyanhewe, and personal email. Running Postfix + Dovecot felt like maintaining a legacy system. I wanted something I could understand end-to-end, configure in one YAML file, and deploy as a single binary. Lightr is that server.

Links

• GitHub Repository